Breathable and liquid impermeable web and method of making the web

ABSTRACT

A method is disclosed for modifying the physical characteristics of a web which involves passing the web between at least one pair of interengaged rolls to incrementally stretch the web, and then withdrawing the incrementally stretched web from between the rolls under tension. A web modified according to the disclosed method has desirable breathability and liquid impermeability, as well as extensibility and a soft, cloth-like textured surface.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.13/446,243, filed Apr. 13, 2012, which is a continuation of U.S.application Ser. No. 12/053,659, now U.S. Pat. No. 8,158,846, filed Mar.24, 2008, which is a continuation of U.S. application Ser. No.10/417,457, now U.S. Pat. No. 7,378,565, filed Apr. 16, 2003, which is adivisional application of U.S. application Ser. No. 09/699,329, now U.S.Pat. No. 6,605,172, filed Sep. 25, 2000, which claims the benefit of aprovisional U.S. Application No. 60/156,900, filed Sep. 30, 1999, thesubstances of which are incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to an improved breathable web and aneconomical method for advantageously modifying the physical propertiesof a web for use as a component of a disposable absorbent article, andto disposable articles incorporating such modified webs.

BACKGROUND OF THE INVENTION

Disposable, wearable articles having an inner, body-facing, liquidpervious component, an intermediate, absorbent, liquid-retainingcomponent and an outer, garment-facing, liquid-impervious component arewell known. Articles of that type are commonly available in the form ofdisposable diapers, disposable underwear, pull-on diapers and trainingpants, incontinence pads, incontinence briefs, sanitary napkins,pantiliners, and the like. Such articles generally include a flexible,liquid-impervious outercover (i.e., backsheet) that is adapted to bepositioned between an absorbent component of the article and theclothing of the wearer, to prevent wetting or soiling of the wearer'sclothing when the article is in use.

In order to provide improved comfort to the wearer of disposableabsorbent articles, certain components of the articles, such as abacksheet, in addition to providing imperviousness to liquids, desirablypermit the passage therethrough of moisture vapor and also preferablyair, to help maintain dryness and to reduce the humidity adjacent thewearer's body. An impervious polymeric film to which breathability hasbeen imparted to allow air and moisture vapor transmission through thefilm is disclosed U.S. Pat. No. 3,156,342, entitled “Flexible AbsorbentSheet,” which issued on Nov. 10, 1964, to G. A. Crowe, Jr.; U.S. Pat.No. 3,881,489, entitled “Breathable, Liquid Impervious Backsheet forAbsorbent Devices,” which issued on May 6, 1975 to Edward WallaceHartwell, et al.; U.S. Pat. No. 3,989,867, entitled “Absorbent DevicesHaving Porous Backsheet,” which issued on Nov. 2, 1976, to James BryantSisson; U.S. Pat. No. 4,153,751, entitled “Process for Stretching anImpregnated Film of Material and The Microporous Product ProducedThereby,” which issued on May 8, 1979, to Eckhard C. A. Schwarz; andU.S. Pat. No. 4,539,256, entitled “Microporous Sheet Material, Method ofMaking and Articles Made Therewith,” which issued on Sep. 3, 1985, toGene H. Shipman.

In addition to imperviousness to liquids, and pervious to moisture vaporand air, the backsheet also preferably includes a cloth-like outersurface, which provides a softer feel, and also a more appealing visualappearance, as compared with the outer surface of a smooth, flat plasticfilm. Two-ply backsheets that provide a desirable, more cloth-likeappearance for such disposable, wearable articles are also known. Inthat regard, U.S. Pat. No. 5,151,092, entitled “Absorbent Article withDynamic Elastic Waist Feature Having a Predisposed Resilient FlexuralHinge,” which issued on Sep. 29, 1992, to Kenneth B. Buell, et al.,discloses a disposable diaper backsheet formed either from a woven or anonwoven material, a polymeric film, or a composite material in the formof a film-coated, nonwoven material. That patent also discloses the stepof embossing of a plastic film backsheet to provide a more cloth-likeappearance to a plastic film.

Also known to those skilled in the art are methods for impartingextensibility to an otherwise substantially inelastic material, whichmay be employed as a backsheet. For example, the use of corrugatingrolls to laterally or longitudinally stretch and to simultaneouslyprovide a corrugated form to thin plastic films is disclosed in U.S.Pat. No. 4,116,892, entitled “Process for Stretching IncrementalPortions of an Orientable Thermoplastic Substrate and Product Thereof,”which issued on Sep. 26, 1978, to Eckhard C. A. Schwarz; U.S. Pat. No.4,834,741, entitled “Diaper With Waistband Elastic,” which issued on May30, 1989, to Reinhardt N. Sabee; U.S. Pat. No. 5,156,793, entitled“Method for Incrementally Stretching Zero Strain Stretch Laminate SheetIn A Non-Uniform manner To Impart A Varying Degree Of ElasticityThereto,” which issued on Oct. 20, 1992, to Kenneth B. Buell et al.;U.S. Pat. No. 5,167,897, entitled “Method for Incrementally Stretching AZero Strain Stretch Laminate Sheet To Impart Elasticity Thereto,” whichissued on Dec. 1, 1992 to Gerald M. Webber et al.; and U.S. Pat. No.5,422,172, entitled “Elastic Laminated Sheet of An IncrementallyStretched Nonwoven Fibrous Sheet and Elastomeric Film and Method,” whichissued on Jun. 6, 1995, to Pai-Chuan Wu. The corrugating rolls disclosedin each of those patents are employed in carrying out a processsometimes referred to as “ring-rolling,” to locally stretch and formcorrugations in the material, in order to impart a greater degree ofstretchability to selected portions of a sheet or web that may serve asa backsheet for disposable absorbent articles. Such backsheets caninclude both a polymeric film and an overlying and contacting layer ofnonwoven, fibrous material.

Although there have been significant product improvements in recentyears that have resulted in improved functioning and increased consumeracceptance of disposable absorbent articles, it is still desirable toprovide an improved material having optimal physical properties relatingto permeability to water vapor and air, and impermeability to liquid.Additionally, the improved material should desirably have the optimalproperties that are particularly useful in an absorbent article, such asgood liquid impact value, and air flow rate. It is further desirablethat the improved material has a soft, cloth-like outer surface andextensibility useful for comfort and fit provided by absorbent articlescontaining such a material.

It would also be advantageous to provide an economical method formodifying a pre-formed web or laminate to have desirable propertieswhich can be used as a structural component or an extensible componentof a disposable absorbent article.

SUMMARY OF THE INVENTION

The present invention provides an improved method of modifying thephysical characteristics of a web at high web speed. The precursor webis passed between at least one pair of interengaged rolls toincrementally stretch the web, then the incrementally stretched web iswithdrawn from between the rollers under tension. An engineering strainrate from about 50 s⁻¹ to about 1650 s⁻¹ is found to be effective inachieving a modified web with desired properties. The method of thepresent invention is applicable at a temperature from ambient to about120° C., and a web speed from about 30 m/min to about 365 m/min.

The modified web has a microporous structure containing few large poresand capillaries. Thus, the resultant microporous web is breathable toair or vapor, but acts as a liquid barrier under the impact pressurecommonly imposed by the wearer of an absorbent article. Particularly,the microporous web has good breathability (as manifested in moisturevapor transmission rate and air flow rate) while maintainingsatisfactorily low leakage under impact pressure. Additionally, themodified web can have a soft, cloth-like surface and extensibility forimproved fit and wearer comfort.

The webs may be films, nonwovens, or composites of films and nonwovenwebs, such as laminates. Typically, the web is made of thermoplasticmaterials which may be a blend of thermoplastic polymers andpore-forming agents such as incompatible organic materials or inorganicparticulate materials. In the incremental stretching process of thepresent invention, the pore-forming agent is activated and the resultantweb has pores and channels (i.e., interconnected pores) through thethickness of its structure, which is generally referred to as a“microporous” web.

The breathable and liquid impermeable web of the present inventioncomprises at least a microporous film and has an MVTR of at least about2000 g/m²/24 hr, a dynamic impact value of less than about 10 g/m², abubble pressure at least about 45 psi, and optionally, an air flow of atleast about 2 liters/m²/s.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic illustration of an exemplary process and apparatusfor modifying a web and imparting breathability to a web in accordancewith the present invention.

FIG. 2 is a fragmentary perspective view of a pair of closely-spacedforming rolls each having alternating and interengaging peripheral teethand grooves.

FIG. 3 is an enlarged, fragmentary, cross-sectional view showing theinterengagement of respective teeth and grooves of the forming rollsshown in FIG. 2.

FIG. 4 is a further enlarged, fragmentary, cross-sectional view showingthe tip portions of the interengaged forming roll teeth with a web ofmaterial positioned between the rolls and spanning and in contact withthe tips of adjacent teeth.

FIG. 5 is an enlarged, fragmentary, cross-sectional view taken along thecross-web direction of a web of material that has passed through a pairof forming rolls such as those shown in FIG. 2.

FIG. 6 is a fragmentary perspective view of a pair of closely-spacedforming rolls having tooth and groove configuration on the surfacewherein one roll has notched teeth and the other roll has unnotchedteeth.

FIG. 7 is a top plan view of web material after it has passed betweenforming rolls having the teeth structure as shown in FIG. 6.

FIG. 8 is an enlarged fragmentary perspective view of a portion of theweb shown in FIG. 7.

FIG. 9 is a schematic illustration of an exemplary process and apparatusfor joining and modifying a composite web material in accordance withthe present invention.

FIG. 10 is an enlarged fragmentary view of a portion of the modified websurface after the web has passed between a set of forming rolls havingalternating teeth and grooves that define a diamond-like pattern.

FIG. 11 is a fragmentary perspective view of a modified web surface,illustrating another forming roll tooth and groove pattern.

FIG. 12 is an enlarged, fragmentary perspective view of another set offorming rolls wherein the upper roll has interrupted teeth and grooveconfiguration having notched teeth, and the lower roll has uninterruptedteeth.

FIG. 13 is an enlarged, fragmentary, diagrammatic, cross-sectional viewof a portion of a microporous film after the film has passed through apair of forming rolls, to impart breathability to the film.

FIG. 14 is an elevational view of apparatus used in a method fordetermining the dynamic impact value of a material as an assessment ofits perviousness to liquids when subjected to impact conditions.

FIG. 15 is a plan view of a disposable diaper that includes structuralcomponents which incorporate a modified web in accordance with thepresent invention.

FIG. 16 is a schematic illustration of the tooling and operatingparameters that contribute to the engineering strain rate.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is directed to the modification of the physicalproperties, and if desired the dimensions, of materials intended for usein disposable absorbent articles. After modification, the material can,if desired, be joined with other materials for incorporation asfunctional and structural elements of disposable absorbent articles.Examples of such materials include precursor films that can be made tobe liquid impervious and breathable, elastomeric films, nonwoven webs,foams, woven webs and the like. Although disclosed herein in the contextof use with disposable articles, it will be apparent to those skilled inthe art that such modified materials also can be employed in otherstructures intended for other uses, including wound dressing, medicaldrapes, surgical gowns, extensible fabrics and garments.

As used herein, the term “extensibility” refers to the degree to whichany material can be stretched, either in the web movement direction orin the cross-web direction, when a tensile biasing force is applied tothe material without catastrophic failure of the material. Theelongation is expressed herein as a percent (%), and is based upon theoriginal, unstretched length and the stretched length immediately beforerupture or failure of the material.

As used herein, the term “extensible” refers to any material that uponapplication of a biasing force is stretchable, or that is elongatable byat least about 50% (i.e., having a stretched, biased length that is atleast about 150% of its relaxed, unbiased length).

As used herein, the term “load to elongate” refers to the biasing forcethat must be applied to any material to elongate it to a givenelongation, either in the web movement direction or in the cross-webdirection, wherein the elongation is expressed as a percent (%), and isthe ratio between the stretched length and the original, unstretchedlength.

As used herein the term “laminate” refers to a material that includestwo or more webs of materials joined to each other to achieve a unitarystructure. The webs can be joined to each other substantiallycontinuously, at spaced-apart locations, or at intermittent points.

As used herein, the term “nonwoven” refers to a fibrous web or sheetthat has a structure of individual fibers or threads that are interlaid,but not in any regular, repeating manner. Nonwoven sheets have in thepast been formed by a variety of processes, such as meltblowing,spunbonding processes, and carded bonding, or combinations thereof.

As used herein, the term “thermoplastic” refers to a polymeric materialwhich can be melted and resolidified with little or no change inphysical properties (assuming a minimum of oxidative degradation).

As used herein, the term “precursor web” refers to a polymeric web priorto being modified such that micropores are provided in the web,particularly in the film component, to allow the web to have increasedbreathability while remaining substantially liquid impervious.

As used herein, the term “breathable film” refers to a film that iscapable of permitting the passage therethrough of moisture vapor andalso preferably air, but that does not permit the passage therethroughof liquids to an undesirable extent.

As used herein, the term “surface contour length” refers to ameasurement along a topographic surface of a material in a specifieddirection.

Modification of Webs

FIG. 1, is a schematic illustration of an apparatus suitable for use inthe method of the present invention for modifying the physical andperformance properties, and if desired the size, of a web. The apparatusand method provide a physically modified web having improved physicalproperties and modified which may be used in disposable absorbentarticles for improved performance and fit/comfort provided by thearticles. Additionally, after being modified in the disclosed apparatusand after having acquired the desired physical properties hereinafterdescribed, such modified webs are capable of being further processed,either alone or together with other materials, and without the modifiedweb experiencing disintegration, rupture, or loss of integrity.

As used herein, the word “web” is intended to encompass continuous rollsand discrete sheets of the materials, though the web in a continuousform is more suitable for high-speed production purposes.

The web has a longitudinal axis that extends along the web movement or“machine” (MD) direction of the web, and a transverse axis that extendsin the cross-web or “cross-machine” (CD) direction of the web.

Referring again to FIG. 1, web 5 is withdrawn from supply roll 4 andtravels in the direction indicated by the arrow. Alternatively, web 5 isformed directly off an extruder equipped with a film die, and optionallya set of tension or take-up rolls between the extruder and formingstation 6. Web 5 is fed to the nip 7 formed by a pair of opposed formingrolls 8 and 9 that together define a first forming station 6. Thestructure and relative positions of forming rolls 8, 9 are shown in anenlarged perspective view in FIG. 2. As shown, rolls 8 and 9 are carriedon respective rotatable shafts 21, 23, having their axes of rotationdisposed in parallel relationship. Each of rolls 8 and 9 includes aplurality of axially-spaced, side-by-side, circumferentially-extending,equally-configured teeth 22 that can be in the form of thin fins ofsubstantially rectangular cross section, or they can have a triangularor an inverted V-shape when viewed in cross section. If they aretriangular, the vertices of teeth 22 are outermost. In any event, theoutermost tips of the teeth are preferably rounded, as shown in greaterdetail in FIGS. 3 and 4, to avoid cuts or tears in the materials, suchas web 5, that pass between the rolls.

The spaces between adjacent teeth 22 define recessed,circumferentially-extending, equally configured grooves 24. The groovescan be of substantially rectangular cross section when the teeth are ofsubstantially rectangular cross section, and they can be of invertedtriangular cross section when the teeth are of triangular cross section.Thus, each of forming rolls 8 and 9 includes a plurality of spaced teeth22 and alternating grooves 24 between each pair of adjacent teeth. Theteeth and the grooves need not each be of the same width, however, andpreferably the grooves have a larger width than that of the teeth, topermit the material that passes between the interengaged rolls to bereceived within the respective grooves and to be locally stretched, aswill be explained hereinafter.

FIG. 3 is an enlarged, fragmentary, cross-sectional view showing theinterengagement of teeth 22 and grooves 24 of the respective rolls. Asshown, generally triangular teeth 22 of one roll extend partially intogenerally triangular grooves 24 of the opposed roll, so that imaginarylines 21 and 23 interconnecting the rounded outer tips of teeth 22 ofrolls 8 and 9, respectively, lie radially inwardly of the rounded outertips of teeth 22 of the opposed roll. The respective axes of rotation ofrolls 8 and 9 so spaced from each other that there is a predeterminedspace or gap between the opposed sidewalls of the interengaged teeth andgrooves of the respective rolls.

FIG. 4 is an even further enlarged view of several interengaged teeth 22and grooves 24 with a web of material being modified therebetween. Asshown, a portion of web 20, which is the modified material of theprecursor web 5 of FIG. 1, is received between the interengaged teethand grooves of the respective rolls. The interengagement of the teethand grooves of the rolls causes laterally spaced portions of web 20 tobe pressed by teeth 22 into opposed grooves 24. In the course of passingbetween the forming rolls, the forces of teeth 22 pressing web 20 intoopposed grooves 24 impose within web 20 tensile stresses that act in thecross-web direction. The tensile stresses cause intermediate websections 26 that lie between and that span the spaces between the tips28 of adjacent teeth 22 to stretch or extend in a cross-web direction,which results in a localized reduction of the web thickness at each ofintermediate web sections 26.

In one embodiment, there is a substantially uniform distribution oflocal strain over the span between adjacent teeth. The portions of web20 that lie between the adjacent teeth are locally stretched while theportions of the web that are in contact the tips of the teeth typicallydo not undergo a similar degree of extension. Not intending to be boundby theory, it is believed that the frictional forces exist between thesurfaces at the rounded outer ends (i.e., tips) of teeth 22 and theadjacent surfaces 28 of web 20 that are in contact therewith. Thefrictional forces reduce the sliding movement of those portions of theweb surfaces relative to the tooth tip surfaces. Consequently, thethickness of web portion 28 that are in contact with the tooth tipsreduces only slightly, as compared with the web thickness reductionsthat occur at intermediate web portion 26.

However, in a typical process according to the present invention, thereis a nonuniform distribution of the local strains over the span betweenadjacent teeth. FIG. 5 illustrates the modified web having a drawnportion 32 which has been fully drawn (i.e., drawn to the natural drawratio of the material), an unstretched portion 30 and an intermediateportion 31. When material is substantially fully drawn in web portion32, no further deformation takes place and no more open areas are beingformed. Thus, the micropores and capillaries are “stabilized” or“fixed”. The area where the web material are being stretched areprimarily in the intermediate portion 31. In the local (i.e., betweenadjacent web portions 30, 31 and 32) stretching process, the webmaterial in the unstretched portion 30 are being incorporated into theintermediate portion 31 where the deformation takes place. Theintermediate portion 31 is typically referred to as the “neck” region.As used herein, the term “neck” refers to the constriction in at leastone dimension by applying a tension force in a direction perpendicularto the desired direction of constriction (which is sometimes called a“neck down”).

The action of pressing of portions of web 20 into the respective grooves24 by teeth 22 therefore causes a non-uniform reduction of the thicknessof web 20 to take place in the cross-web direction of the web.Accordingly, web 20 undergoes a greater reduction in thickness in thecross-web portions of the web that extend between and that span adjacentteeth 22 than it undergoes at those cross-web portions of the web thatare in contact with the surfaces at the outer ends of teeth 22. Thus, byvirtue of passing through the interengaged rolls and being locallylaterally stretched at spaced intervals between adjacent teeth, theupper and lower surfaces of the web after it passes from between theopposed rolls define modulating surfaces that are the mirror images ofeach other when the web is viewed in cross section in the cross-webdirection, as shown in FIG. 5. Modulating upper and lower surfaces ofthe web include alternating peaks 30 and valleys 32, which definealternating heavy and light basis weight regions. The light basis weightregions are found at the positions of the web wherein the web materialhas been locally laterally stretched. The localized stretching of theweb in the cross-web direction results in a wider (as manifested in theincrease in the surface contour length) modified web that has aplurality of spaced, longitudinally-extending, localized areas ofreduced web thickness. Additional cross-web stretching of the exiting,formed web can be effected by passing the modified web between so-calledMount Hope rolls, tentering frames, angled idlers, angled nips, and thelike (not shown), each of which is known to those skilled in the art.

Because of the localized cross-web stretching of web 5 that has takenplace, with the consequent increase in web width, the modified web 20that exits from the forming rolls at first forming station 6 has a lowerbasis weight than that of the entering precursor web 5, provided theexiting material remains in a substantially flat, laterally extendedstate. The laterally-stretched web as it exits from between the formingrolls may contract laterally to its original width. When the web isplaced under some tension in the web movement direction, the exiting,modified web may have the same basis weight as it had in its enteringcondition. If the exiting modified web is subjected to a sufficientlyhigh web movement direction tension, the exiting modified web can bemade to contract to a smaller width than its original width, in whichcase the web will have a greater basis weight than its original basisweight. On the other hand, if the web is subjected to sufficientadditional cross-web stretching by passing the modified web betweenso-called Mount Hope rolls, tentering frames, angled idlers, anglednips, or the like as described above, the exiting, modified web willhave less than its original basis weight. Thus, by selecting a suitableforming roll tooth and groove configuration, by selecting a suitable webmovement direction tension level, and by selecting whether or not tosubject the web to additional cross-web stretching, the resultingmodified web can have a web width that can range from about 25% to about300% of the unmodified, precursor web width and a basis weight that isless than, equal to, or greater than the unmodified, precursor web'soriginal basis weight.

Teeth 22 and grooves 24 can be generally triangular in cross section, asshown in FIG. 3, and preferably each of teeth 22 is of the same size sothat each of the opposed teeth and grooves on respective forming rolls8, 9 interengage with each other along the entire axial lengths of eachof the rolls. In one embodiment, teeth having a peak-to-peak pitch ofthe order of about 0.030 to 0.100 inches, having sidewalls disposed atan included angle of the order of about 9° to 12°, and having atip-to-base tooth height and groove depth of the order of about 0.060 to0.300 inches can be employed in carrying out the present invention. Aswill be appreciated by those skilled in the art, the sizes of therespective teeth and grooves can be varied within a wide range and wouldstill be effective to carry out the present invention. In that regard,additional structural details of suitable forming rolls are provided inU.S. Pat. No. 5,156,793, entitled “Method for Incrementally StretchingZero Strain Stretch Laminate Sheet in a Non-Uniform Manner to Impart aVarying Degree of Elasticity Thereto,” which issued on Oct. 20, 1992, toKenneth B. Buell et al.; in U.S. Pat. No. 5,167,897 entitled “Method forIncrementally Stretching a Zero Strain Stretch Laminate Sheet to ImpartElasticity Thereto,” which issued on Dec. 1, 1992, to Gerald M. Webberet al.; and in U.S. Pat. No. 5,518,801, entitled “Sheet MaterialsExhibiting Elastic-Like Behavior,” which issued on May 21, 1996, toCharles W. Chappell et al., the disclosures of each of which patents arehereby incorporated by reference herein.

If the web is expanded only in the X-Y plane, there will be asubstantial decrease in the basis weight of the modified web, whichserves to reduce the cost of any components of which the modified web isa part. Preferably, the width of the modified web of the presentinvention is about 100% greater than the original width of theunmodified, precursor web. On the other hand, if the web movementdirection (MD) tension on the modified web as it exits the forming rollsis sufficiently high, the modified web will have a width that is lessthan its original width, and a greater basis weight than that of theunmodified, precursor web.

FIG. 6 shows another configuration of opposed forming rolls, which canbe used to expand portions of the web in the web thickness dimension,that is, by expanding portions of the web out of the X-Y plane into theZ-direction. As shown in FIG. 1, an unmodified web 5 is fed from asupply roll 4 into the nip 7 of opposed forming rolls 70 and 72 whichdefine forming station 6. Roll 70 includes a plurality ofcircumferentially-extending, axially-spaced circumferential teeth 75.However, unlike continuous circumferential teeth 22 of forming roll 8shown in FIG. 2, circumferential teeth 75 of roll 70 include a pluralityof circumferentially-spaced ridges 74, and interveningcircumferentially-spaced notched regions 78 that define recessed, openregions on teeth 75. As shown in FIG. 6, notches 78 on respectiveaxially adjacent circumferential teeth 75 are aligned laterally todefine a plurality of circumferentially-spaced groups of notched regions78 about the periphery of roll 70. The respective laterally-extendinggroups of notched regions each extend parallel to the axis of roll 70.

Roll 72 is similar in overall construction to forming rolls 8 and 9 asshown in FIG. 2 in that roll 72 includes a plurality ofcircumferentially-extending, axially-spaced teeth 79 that extend incontinuous, uninterrupted form about the circumference of the roll.Teeth 79 of roll 72 intermesh with teeth 75 of roll 70. But the portionof the web that passes between the notched regions 78 of roll 70 and theteeth 79 of roll 72 will be unformed, i.e., the web will not be deformedor stretched in that area and will remain substantially planar, whilethe portions of the web passing between ridges 74 of roll 70 and theteeth 79 of roll 72 will be deformed or stretched beyond the elasticlimit of the web, resulting in a plurality of raised, rib-like elements.The raised, rib-like elements on the modified web provides a cloth-liketexture, which improves the comfort and feel of the absorbent articlecontaining such cloth-like, texturized web.

The forming rolls suitable for use herein to provide z-directionexpansion in the modified web may have various tooth and grooveconfigurations on the surface of the forming rolls. Typically, the teethare spaced, circumferentially extending ridges (FIG. 2). The teeth mayhave circumferentially spaced notches in the ridges, producing spaced,rectangular arrays of raised ribs in the z-direction in the resultingmodified web (FIGS. 7 and 8). More detailed descriptions andillustrations of the texturizing/forming rolls can be found in U.S. Pat.No. 5,518,801, issued May 21, 1996 to Chappell et al.; U.S. Pat. No.5,650,214, issued on Jul. 22, 1997 to B. J. Anderson et al.; thedisclosures of which are hereby incorporated by reference.

Referring now to FIGS. 7 and 8, there is shown a portion of a modifiedweb 20 which has passed between a pair of opposed, interengaged formingrolls 70 and 72 having the tooth configurations shown in FIG. 6. Web 20has two centerlines, a longitudinal centerline, which is also referredto hereinafter as an axis, line, or direction “l” and a transverse orlateral centerline, which is also referred to hereinafter as an axis,line, or direction “t”. The transverse centerline “t” is generallyperpendicular to the longitudinal centerline “l”.

Web 20 includes a network of distinct regions. The network includes atleast a first region 98, a second region 92, and a transitional region87, which is at the interface between the first region 98 and the secondregion 88. Web 20 also has a first surface 93 a and an apposite-facingsecond surface 93 b. In the embodiment shown in FIGS. 7 and 8, web 20includes a plurality of substantially flat, longitudinally spaced firstregions 98 and a plurality of alternating second regions 88.

First regions 98 have a first, transversely-extending axis 89 and asecond, longitudinally-extending axis 91, wherein the first axis 89 ispreferably longer than the second axis 91. The first axis 89 of thefirst region 98 is substantially parallel to the transverse axis of web20, while the second axis 91 is substantially parallel to thelongitudinal axis of the web.

Second regions 88 have a first, transversely-extending axis 95 and asecond, longitudinally-extending axis 94. The first axis 95 issubstantially parallel to the transverse axis of the web, while thesecond axis 94 is substantially parallel to the longitudinal axis of theweb. In the preferred embodiment of FIGS. 7 and 8, the first regions 98and the second regions 88 are substantially linear, each extendingcontinuously in a direction substantially parallel to the longitudinalaxis of the web.

In the embodiment shown in FIGS. 7 and 8, first regions 98 aresubstantially planar. That is, the material within first regions 98 issubstantially flat and is in substantially the same condition after themodification step undergone by web 20 by passage between interengagedrolls 70 and 72 shown in FIG. 6 as it was in before the web was passedbetween the forming rolls.

Second regions 88 include a plurality of raised, rib-like elements 90that have a first or major axis 94 that is substantially parallel to thelongitudinal axis of the web 20, and a second or minor axis 95 that issubstantially parallel to the transverse axis of web 20. The dimensionof rib-like elements 90 along first axis 94 is at least equal to, andpreferably longer than, the dimension along second axis 95. Preferably,the ratio of the dimension of rib-like elements 90 along first axis 94to the dimension along second axis 95 is at least 1:1, and morepreferably at least 2:1 or greater. Further, rib-like elements 90 insecond region 92 are adjacent one another and are separated from eachother by an unformed area 98 having a width in the directionperpendicular to the major axis 94 of the rib-like elements. Thedimensions of the rib-like elements can also be varied, if desired. Amore detailed description of a web having first and second regions asshown in FIGS. 7 and 8 is provided in U.S. Pat. No. 5,518,801, thedisclosure of which has already been incorporated herein by reference.

Other arrangements of the teeth and grooves on the forming rolls knownto those skilled in the art are also contemplated by the presentinvention. For example, the teeth may be arrangement in groups ofrectangular arrays, wherein each group has several teeth and therespective groups of teeth are separated by an intervening gap that isdevoid of teeth (FIG. 12). Additionally, the forming rolls may havedecorative shapes, either as protruding teeth or as recessing grooves,on the roll surface. Nonlimiting examples of the decorative shapesinclude geometric shapes, animal shapes, floral or botanical shapes,cartoon figures.

In addition to the surface patterns illustrated in FIGS. 7 and 8 in theform of ridges and grooves, all of substantially equal lengths to definegenerally rectangular areas of deformation, the desired stretching orthinning of a web can, if desired, be effected by other forming rolltooth and groove configurations that can cause localized stretching ofthe material. For example, as shown in FIG. 10, instead of spacedrectangular arrays of ridges and grooves the deformation pattern can bein the form of ridges and grooves defining an array of spaced,diamond-shaped elements 100 with intervening undeformed areas 102. Eachsuch diamond-shaped element is defined by alternating rib-like elements106 and intervening grooves 104. Examples of methods and apparatus forformation of such diamond-shaped elements are disclosed in U.S. Pat. No.5,650,214, entitled, “Sheet Materials Exhibiting Elastic-Like Behaviorand Soft, Cloth-Like Texture”, which issued on Jul. 22, 1997, to BarryJ. Anderson, et al., the disclosure of which is incorporated herein byreference.

As shown in FIG. 11, the deformation pattern can also be in the form ofridges and grooves that together define an array of spaced,circularly-shaped elements 108. Each such circular element can bedefined by varying-length rib-like elements 114 and intervening grooves112. Between respective circularly-shaped elements 108 are unformedintervening areas 110. As will be apparent to those skilled in the art,other deformation patterns can also be employed, if desired, such asthose illustrated and described in U.S. Pat. No. 5,518,801, thedisclosure of which was earlier incorporated herein by reference.

Another set of forming rolls, having a different arrangement of theperipheral teeth and grooves and that can be utilized in the practice ofthe present invention, is shown in FIG. 12. Forming roll 150 is similarto forming roll 70 shown in FIG. 6 except that thecircumferentially-extending teeth 75 are provided in respective groups152, each group containing several teeth 75. Each of groups 152 of teeth75 is spaced from an adjacent group of teeth in the axial direction ofthe roll, and the respective groups of teeth are separated by anintervening gap 154 that is devoid of teeth. Forming roll 72 of FIG. 12has the same configuration as forming roll 72 of FIG. 6.

Because of the general structural similarity of the teeth and grooves onthe several forming rolls shown in FIGS. 2, 6, and 12, the samereference numerals have been applied to corresponding parts of the rollsshown in FIGS. 2, 6, and 12.

In addition to modifying the dimensions of a web by extending the web,for example, in the X-Y plane to lower its basis weight, and by addingloft to the web in the Z direction, the present invention is alsodirected to modifying the physical properties of the web in a beneficialway. As used herein the term “physical properties” refers to theperformance characteristics of the web, including the strength of theweb when subjected to a tensile force, its extensibility when subjectedto a tensile force, and the force needed to elongate the web to a pointshort of tearing or rupture of the web material. The term “physicalproperty” also includes web characteristics that relate to theperformance of the web used as a component of an absorbent article, suchas moisture vapor transmission rate (MVTR), dynamic fluid impact value,bubble pressure and air flow rate. Those desirable physical propertymodifications can be achieved by passing the web through at least onepair of the interengaged forming rolls that have been described herein,and optionally, applying some tension in the web-movement direction.Additionally, the present invention also encompasses successivemodifications of the web by passing the web through successive sets offorming rolls, tensioning and, if desired, additional cross-webdirection stretching. For example, a first set of forming rolls canserve to increase the extensibility of the web without causing shreddingor tearing of the web, and a second set of forming rolls can serve toexpand the web in the X-Y plane.

When the web materials, such as nonwoven webs, films, or laminatesthereof, are incorporated in a disposable absorbent article, it istypical that the cross-web (CD) strength of the modified web of thepresent invention be substantially lower than that of an unmodified web.It is also typical that the cross-web extensibility of a modified web ofthe present invention is substantially higher than that of an unmodifiedweb. It is further typical that the load to elongate of a modified webof the present invention is substantially lower than the typical valuesattainable from commercially available, nonwoven webs. A modified web ofthe present invention exhibits (1) a load to achieve 10% cross-webelongation of from about 5% to about 100% of the corresponding cross-webelongation load of the unmodified web; (2) a load to achieve 30%cross-web elongation of from about 5% to about 100% of the correspondingcross-web elongation load of the unmodified web; and (3) a cross-webextensibility of from about 105% to about 200% of the cross-webextensibility of the unmodified web. Such an extensible web more easilybe conforms with and adapts to the contours of the body of a wearer of adisposable article, both during application of the article to the bodyas well as while being worn and being subjected to loads as a result ofbody movements of the wearer. The improved fit and adaptability tochanging wearing conditions leads to greater wearer comfort.

Suitable nonwoven webs are typically prepared from fibers ofthermoplastic polymers such as polyolefins, polyesters, polyamides,cellulose derivatives such as rayon, and copolymers and mixturesthereof. Preferably, the nonwoven webs are made of polyolefins such aspolyethylene, polypropylene, polybutylene, and their copolymers. Thefibers may be of a single polymer or of a blend of polymers. Thenonwoven web may be made of fibers having different compositions.Bi-component fibers made from two different polymers or blends, arrangedin a sheath-core, or side-by-side configuration, are also suitable foruse herein. Also useful herein are bi-component fibers having asheath-core structure with a lower melting polymer or blend in thesheath. For example, the fiber may have a sheath of polyethylene and acore of polypropylene and copolymer, or polyester and copolymers. Thenonwoven web may be made by processes known to those skilled in the art,including carding, meltblowing, spunbonding and combinations thereof.

Modified web materials may be incorporated into a disposable absorbentarticle, including nonwoven webs, polymeric films, and laminates orother composite structures thereof. For example, a modified web can beutilized as a component of a composite, breathable backsheet, one thatis liquid impervious but that is pervious to gases and moisture vaporand that preferably has at least one soft, cloth-like outer surface.

Modification of a Web Containing Pore-Forming Agents

When an unmodified web is a film containing pore-forming agents orincompatible fillers, the modification process and apparatus disclosedherein advantageously impart breathability to the modified film whileimparting minimal adverse effect on the leakage performance of themodified web. Breathability can be imparted to a polymeric film, whilemaintaining its imperviousness to liquids, by forming micropores in thefilm. The desired micropores should be sufficiently small in order toprevent the passage therethrough of liquids, but they are large enoughfor the passage therethrough of air and moisture vapor. Micropores canbe formed directly in an otherwise solid film in several ways, includingperforating the film as disclosed in U.S. Pat. No. 3,881,489, entitled“Breathable, Liquid Impervious Backsheet for Absorbent Devices”, whichissued on May 6, 1975, to Edward Wallace Hartwell. Perforations can beprovided by mechanically puncturing the film, but that techniquerequires close tolerance control over the puncturing elements of theapparatus, which over time might provide micropores of increasinglygreater size as a result of mechanical wear of the puncturing elements.Larger pores could allow the undesired passage of liquids through suchfilms.

Another way to enable the formation of micropores in an otherwiseimpervious film involves substantially uniformly dispersing pore formingagents within a thermoplastic polymer matrix. The dispersion of the poreforming agents can be effected by a mixing step, and the resultingmixture can be formed into a thin film by extruding, casting, or blowingtechniques that are known to those skilled in the art. The pore formingagents include incompatible organic materials and inorganicparticulates. As used herein, the term “incompatible” means organic orinorganic materials that are incapable of being dissolved in thepolymer, so that those materials retain their original form andcomposition and remain separate and distinct from, but are surroundedby, the polymer matrix. Formation of the micropores is effected afterthe film has been modified, by locally stretching the precursor film ina manner that is described in detail hereinafter.

Nonlimiting examples of incompatible organic materials includepolystyrenes, polycarbonates, polyacrylates, fluorocarbon polymers orlow melting resins, polyterephthalates, and copolymers and mixturesthereof. The preferred incompatible organic materials as pore formingagents are polystryene and copolymers. Another exemplary organicmaterial that can be used as a pore forming agent is mineral oil, asdisclosed in U.S. Pat. No. 4,609,584, entitled “Absorptive Devices,”which issued on Sep. 2, 1986, to Cutler et al., the disclosure of whichis incorporated herein by reference.

Nonlimiting examples of inorganic materials that can be used as poreforming agents include calcium carbonate, titanium dioxide, clays,silicas, zeolites, kaolin, mica, carbon, and mixtures thereof. Calciumcarbonate is a preferred inorganic particulate material because it ischeap and commercially available. Preferably, the inorganic particle issupplied in particulate form, having a particle size ranging from about1 to about 5 microns, and it can constitute from about 5 to about 70percent by weight of the polymer-particulate mixture. The inorganicparticle can optionally be coated with a fatty acid ester to enablehigher loadings of the inorganic particle to be included in thepolymer-inorganic mixture. Suitable other inorganic particles aredisclosed in U.S. Pat. No. 4,472,328, entitled “Process for ProducingPorous Film or Sheet,” which issued on Sep. 18, 1984, to Sugimoto etal., and in U.S. Pat. No. 4,777,073, entitled “Breathable Films PreparedFrom Melt Embossed Polyolefin/Filler Precursor Films,” which issued onOct. 11, 1988, to Sheth, the disclosures of both patents areincorporated herein by reference.

Typically, the pore forming agents comprises at least about 5 wt % ofthe polymer, preferably from about 10 wt % to about 70 wt %, morepreferably from about 20 wt % to about 60 wt %, and most preferably fromabout 30 wt % to about 50 wt %. The average size of the pore formingagents should be less than about 50 microns, preferably less than about10 microns and more preferably less than 5 microns. The sizedistribution of the pore forming agents should be such that less than10% of the agents have a size greater than 50 microns.

Mixing of the pore forming agents and the thermoplastic polymer can beeffected in any suitable mixing device, such as a mixing extruder, toobtain a substantially uniform mixture of the components. Preferably,the pore forming agents are substantially uniformly dispersed throughoutthe polymeric matrix material. A flexible precursor film having athickness of the order of from abut 0.3 mils to about 5 mils can beformed from such a mixture using known film forming equipment andtechniques.

Suitable polymers for use herein in a film of the present inventioninclude thermoplastic polyolefins, such as polyethylene, polypropylene,polybutylene, and their copolymers and mixtures thereof. Various typesof polyethylenes such as low density polyethylene, ultra-low densitypolyethylene, linear low-density polyethylene, and high-densitypolyethylene are suitable polyethylenes for backsheets. Other suitablefor use herein include, but not limited to, INSITE, available from DowChemical Company, of Midland, Mich., or EXXACT, available from the ExxonChemical Company, of Bay City, Tex.

Other suitable thermoplastic polymers include polyesters, polyurethanes,polyamides, compostable or biodegradable polymers, heat-shrinkablepolymers, thermoplastic elastomers, and metallocene-catalyst-basedpolymers, copolymers of the above-mentioned polymers, and mixturesthereof. Nonlimiting examples include polyurethanes such as ESTANE,available from B.F. Goodrich & Company of Cleveland, Ohio, andPELLETHANE, available from Dow Chemical Company of Midland, Mich.;polyamides such as PEBAX, available from Elf Atochem of Philadelphia,Pa.; polyesters such as HYTREL, available from DuPont de Nemours &Company of Wilmington, Del., ARNITEL, available from DSM EngineeringPlastics of Evansville, Ind., and ECDEL, available from Eastman Companyof Kingsport, Tenn. Exemplary compostable or biodegradable polymers aredisclosed in U.S. patent application Ser. No. 09/520,676, filed on Mar.7, 2000, and in U.S. provisional patent application (Attorney docket no.8209P) filed on Aug. 17, 2000, both in the name of Zhao et al., thedisclosure of which is hereby incorporated by reference.

Some of these polymeric films are breathable via activated diffusion ofthe moisture vapor through favorable molecular interactions andmolecular architecture of the polymeric material. The breathability ofsuch polymeric films can be further improved by creating micropores inthe film using the process disclosed herein, whereby the moisture vaporcan be more readily transmit through the apertures, voids, or pores.

A particularly suitable film 11 is a linear, low density polyethylenefilm that can have a thickness of from about 0.25 mils to about 5 mils,preferably a thickness of from about 0.25 mils to about 2.5 mils, andmost preferably a thickness of from about 0.5 mils to about 1.5 mils.

In carrying out a method of making a composite, breathable, cloth-likebacksheet in accordance with the present invention, breathability can beimparted to precursor film 11 before attachment of the film to nonwovenweb 9, subsequent to its attachment to the nonwoven web, or both priorto and, if desired, subsequent to its attachment to the nonwoven web.The precursor film and/or the precursor film/nonwoven composite can beactivated at modification station 16 to provide breathability to theprecursor film by passing the film or the composite between a pair ofopposed, interengaged forming rolls 14, 17 having any of the rollstructures and roll surface configurations generally described earlierherein and shown in FIGS. 2, 6, 10, 11, and 12. The passing between suchforming rolls of the precursor film, or of the precursor film andnonwoven laminate, can be repeated any number of times, and in anycombination of the forming roll patterns hereinbefore described, untilthe desired composite web properties are attained.

When a precursor film is passed between forming rolls having rollsurface configurations of any of the types described herein, theinteractions between the roll surface and the film provide localizedstretching of the precursor film which results in the formation ofmicropores in the film. FIG. 13 shows a film after micropores have beenformed, the polymeric component 40 of the film is extensible to acertain degree without rupture, whereas the pore forming agent 42 of thefilm is not extensible to any significant degree. Initially, polymericcomponent 40 provides a polymeric matrix that substantially completelysurrounds and contacts the outer surfaces of pore forming agents 42.When the precursor film is stretched by a local incremental tensileforce, such as by passage of the film between interengaged forming rollsof the types hereinbefore described, the extensible polymeric component40 of the film becomes stretched locally. As a result, the polymericcomponent pulls away from and ultimately at least partially separatesfrom some of the surfaces of the substantially inextensible pore formingagents 42 to cause the formation of a plurality of local voids or openareas 44 that are devoid both of the polymer and of the pore formingagent. The separation occurs at portions of the interfaces betweenpolymeric component 40 and the peripheral surfaces of pore formingagents 42, most likely at the weak interfacial bonding sites betweenthem. Typically, the micropores are irregularly configured and areirregularly distributed throughout the stretched areas of the film.

The micropores that are so developed by stretching the precursor filmare of such a size that they are sufficiently large to permit passagethrough the film of air and moisture vapor, imparting the attribute ofbreathability to the film. However, preferably they are not so large asto allow the passage of liquids through the film. Thus, the microporespreferably have a mean pore size of less than about 0.4 microns, andmore preferably less than 0.3 microns. In a preferred embodiment, themean pore size may range from about 0.1 microns to about 0.25 microns.

The distribution of open areas 44 is also preferably such that at leastsome of the open areas are in communication with other, adjacent openareas to define flow paths that extend through the modified film fromone surface to the other. In that respect, the interconnected microporescreates a capillaries system within the modified film to allowbreathability, that is, permitting the passage of air and moisturevapor. The larger the pores/capillaries, the higher the breathability.However, for a web suitable for use as a breathable component (e.g., abacksheet) of an absorbent article, it must also be substantiallyimperviousness to the passage of liquids therethrough. If thecapillaries are too large, there would be no meaningful discriminationbetween liquid permeability and water vapor/air permeability. Thus,there needs to be a balance between increasing breathability andmaintaining liquid impermeability.

Furthermore, if the capillaries are small and hydrophobic. A certainamount of pressure is needed to fill the small capillaries with water.The smaller the capillary, the greater the pressure required to forcethe liquid into the capillary. The pressure of particular concern isthat encountered by an absorbent article during wear, which may beimposed by wearer's motions such as sitting, lying, bending. Thus, for amodified web to simultaneously provide breathability and satisfactoryleakage performance, the large capillaries in the web should be smallenough such that they do not get filled with fluid under the pressureencountered during wear. In that respect, a few large capillaries arelikely to have significantly adverse effect on the impact leakageperformance of the modified web. Thus, the average pore/capillary sizesare not as indicative of leakage performance as the population of thelarge size pores/capillaries. The preferred microporous web should havefew large capillaries, preferably the capillary diameters are less than0.3 microns, more preferably less than 0.2 microns, and most preferablyless than 0.1 microns. It is known that both the capillary diameter andthe surface tension between the fluid and the capillary walls affect theleakage performance. Therefore, the web should preferably be made ofhydrophobic material which provides a sufficiently high surface tensionwithin the capillary to resist being filled by liquids at low pressures.Webs made of polyolefin polymers or blends are generally hydrophobic andare particularly preferred.

The incremental stretching process using the roll configurationsdisclosed herein is particularly useful for modifying the web to achievethe balanced properties of breathability and liquid impermeability,because fewer large pores and capillaries are formed by the incrementalstretching process. It is found that further improvements in propertiescan be achieved by controlling certain process parameters. For example,applicants have found that by heating the web to a sufficienttemperature above ambient while undergoing the incremental stretchingoperation and controlling other process parameters such as local strainrate, tooling parameters, and web speed, particularly beneficial resultscan be obtained. Most significantly, the properly controlled processparameters suppress or reduce the formation of large pores/capillariesthat are detrimental to fluid imperviousness.

As discussed above, in an incremental stretching process of the presentinvention, there is a nonuniform distribution of local strains over thespan between adjacent teeth, resulting in an unstretched web portion 30,a drawn portion 32 and an intermediate or neck portion 31. Applicantshave found that the pore initiation and growth in the neck regionfollows a “rapid nucleation” mode. That is, multiple micropores areinitiated simultaneously by the pore forming agents dispersed in thepolymeric matrix material. As such, the total applied stress isdistributed substantially uniformly among the growing micropores. Theresulting microporous web tends to have a multiplicity of relativelysmall pores of fairly uniform sizes, and the network of capillariesformed thereof is also of uniform diameters. As discussed above, such amicroporous web has good breathability and good fluid impermeability.

In contrast, in a non-incremental stretching process where stresses areapplied at far-apart or peripheral portions of a web, the web materialis uniformly stretched without much necking. The pore initiation andgrowth in the uniformly stretched material follows a “slow nucleation”mode. A few micropores are initiated by the pore forming agents. Thesepore initiation sites become the weak or stress concentration points,leading to accelerated pore growth at these sites. Thus, the webmaterial undergoes different pore growth rates at different sites. Theresultant microporous web has inhomogeneous pore sizes and channeldiameters; the early pore initiation sites have becomedisproportionately large. Such a web is highly breathable, but it alsotends to have serious leakage problem. Exemplary non-incrementalstretching process include tentering or rolling with toothless rolls.

One process parameter that can be used beneficially in the modificationprocess disclosed herein is the temperature of the web being modified.It is found that when the web is modified at a temperature sufficientlyabove ambient, the intermediate web portion 31, where the deformation ofthe web material and pore initiation/growth occur, expands. Thus, moreof the favorably-sized pores and channels are formed in the wider neckzone in the intermediate web portion, resulting in higher breathabilitywhile maintaining the liquid impermeability. The web temperature shouldtypically be at least about 45° C., preferably at least about 55° C. andmore preferably at least 65° C. The elevated web temperature can beachieved by preheating the web, heating the tooling, or both. Dependingon the polymeric material used in the web, the temperature of the webshould not be so high such that the web softens or melts to the extentthat the web loses its mechanical strength substantially. Typically, theweb temperature should be no more than about 120° C., preferably no morethan about 105° C., and more preferably no more than about 90° C. Forwebs of polyolefin materials, a web temperature ranging from about 45°C. to about 95° C. is preferred.

Another useful process parameter is the engineering strain rate ascalculated below. In a modification process according to the presentinvention, a precursor web passes between at least one pair ofinterengaging rolls where the teeth on the roll surface stretch the webincrementally. FIG. 16 shows a representative geometry for teeth on twointerengaging rolls, wherein R_(T1) and R_(T2) are the tip radii of theteeth profiles, P is the tooth pitch, and E is the depth of engagement.

The engagement depth E is a function of time:

${E(t)}:={E - {{Di} \cdot {\left\lbrack {1 - {\cos \left\lbrack {{\left\lbrack \frac{t}{\left( {2 \cdot T} \right)} \right\rbrack \cdot \left( {2 \cdot {{acos}\left( {1 - \frac{E}{Di}} \right)}} \right)} - {{acos}\left( {1 - \frac{E}{Di}} \right)}} \right\rbrack}} \right\rbrack.}}}$

wherein Di is the roll diameter, and t has a value ranging from zero (atthe initiation of engagement) to T (at total engagement or just prior tothe initiation of disengagement). T can be calculated as below:

$T:={{{acos}\left( {1 - \frac{E}{Di}} \right)} \cdot {\frac{Di}{2 \cdot {Vw}}.}}$

The average local strain, Strain(t), is dependent on the pitch P, thelength between the tangent of the tooth tips L(t) and the wrap length ontooth tips S(t):

${L(t)}:={{\left\lbrack {\left( {{E(t)} - {{RT}\; 1} - {{RT}\; 2}} \right)^{2} + \left( {0.5 \cdot P} \right)^{2} - \left( {{{RT}\; 1} + {{RT}\; 2}} \right)^{2}} \right\rbrack^{0.5}.{S(t)}}:={{{\left( {{{RT}\; 1} + {{RT}\; 2}} \right)\begin{bmatrix}{3.14159 - {{atan}\left\lbrack {0.5\frac{P}{\left( {{E(t)} - {{RT}\; 1} - {{RT}\; 2}} \right)}} \right\rbrack} -} \\{{acos}\left\lbrack \frac{\left( {{{RT}\; 1} + {{RT}\; 2}} \right)}{\left\lbrack {\left( {{E(t)} - {{RT}\; 1} - {{RT}\; 2}} \right)^{2} + \left( {0.5P} \right)^{2}} \right\rbrack^{0.5}} \right\rbrack}\end{bmatrix}}.{{Strain}(t)}}:={\left\lbrack {\frac{2 \cdot \left( {{L(t)} + {S(t)}} \right)}{P} - 1} \right\rbrack \cdot 100.}}}$

The average local strain rate can be calculated by taking the derivativeof the average local strain, and the engineering strain rate iscalculated by setting the second derivative of the average local strainto zero (i.e., the maximum of the average local strain rate versus timecurve). As shown above, the engineering strain rate is a function ofseveral tooling and operating variables, including roll diameter,tooling pitch (which determines the span between neighboring teeth),depth of engagement of the teeth, roll diameter, web speed (whichdetermines the engagement speed), and tooth tip radius. Exemplary rollssuitable for use herein may have diameters of about 6 to about 24 inches(15.24 to 60.96 cm), tooth pitch of about 0.030 to about 0.100 inch(0.762 to 2.54 mm), and tooth tip radius of about 0.004 to about 0.006inch (0.102 to 0.152 mm).

Modified web having satisfactory properties (such as water vapor/airbreathability and liquid impermeability) can be obtained via a localstretching process at room temperature when the engineering strain rateis optimized. For example, a polyolefin web can be modified to havedesirable moisture vapor transmission rate (MVTR) and liquid impactvalue. Typically a MVTR of at least 2000 g/m²/24 hr and a liquid impactvalue of less than 10 g/m² can be achieved when the web is modified at atemperature from ambient to 110° C., and preferably from about 45° C. toabout 95° C., and an engineering strain rate in the range from about 50s⁻¹ to about 1650 s⁻¹, preferably from about 150 s⁻¹ to about 1100 s⁻¹,and more preferably from about 350 s⁻¹ to about 900 s⁻¹. Modified webhaving desirable properties can be achieved at a minimum web speed ofabout 30 m/min, and a maximum web speed up to about 150 m/min,preferably up to 300 m/min and more preferably up to 365 m/min. Thus,the present invention provides an economic method of manufacturing abreathable, liquid impermeable and cloth-like web at high line speed.

Joining Nonwoven Web with Film to Form a Laminate

FIG. 9 shows another aspect of the present invention the joining to onesurface of a nonwoven web 5 at joining station 13 of a polymeric film 11to provide a composite web 12 that can be utilized as a backsheet for adisposable absorbent article, such as a disposable diaper, or the like.Film 11 can be a polyolefin film, preferably a polyethylene film, andforms one layer of a composite backsheet that includes aliquid-impervious barrier film and at least one layer of a thin,nonwoven sheet that is attached to at least one surface of the film.

One or both web 5 and polymeric film 11 of FIG. 9 may be a precursor webor film which can be modified to have increased breathability bysuitable treatment of the web or film as described in the presentinvention. Alternatively, one or both web 5 and polymeric film 11 may bemodified prior to being joined into a laminate.

The film material can be joined to the nonwoven material at joiningstation 13 in a number of ways, including thermal lamination, adhesivelamination, direct lamination by extrusion, and vacuum lamination, eachof which methods is well known to those skilled in the art. The filmmaterial can be a pre-formed film and can be modified, as previouslydescribed, to impart breathability at a time before it is joined withthe nonwoven material. Preferably, film 11 and nonwoven 5 are joinedbefore the film is made breathable, after which the resulting compositeweb 12 can be passed between suitable forming rolls at modificationstation 16 to locally stretch the composite web, thereby providebreathability to the film component of the composite web. This allowsthe properties of the nonwoven web to be modified as desired withoutsimultaneously undesirably effecting the structural integrity of thefilm and/or the composite.

The joining of a non-fibrous polymeric film with a fibrous nonwoven webto form a composite web can be effected by heating either or both of theweb or film to its softening temperature, and then pressing the web andfilm together lightly so that the web and film adhere to each othersufficiently to form a coherent, unitary, composite web upon cooling.Pressing can be performed at joining station 13 shown in FIG. 9.Alternatively, instead of heating one or both the web or the film, thecomponents of the composite web can be joined by applying to either ofthe materials a suitable adhesive, such as adhesive H2511, availablefrom Findley Adhesives, Inc., of Milwaukee, Wis., and by then lightlypressing the materials together at joining station 13 so that theyadhere to each other sufficiently to form a coherent composite web afterthe adhesive sets. When adhesive is utilized to join the materialstogether, the adhesive is preferably applied to one or both of thematerials in a discontinuous pattern, in order not to completely coat anunactivated precursor film, and in order not to fill all the microporesat the surface of a previously-activated precursor film.

As a further variant of the method of joining a polymeric precursormaterial with a nonwoven web, a layer of polymeric precursor materialcan be extrusion coated onto one of the surfaces of the nonwoven web. Inthat instance, because of the elevated temperature of the polymericmaterial as it exits from an extruder onto the nonwoven web, theextruded material is sufficiently tacky so that it adheres to at leastportions of the surface of the nonwoven web. If the temperature of theextruded material is sufficiently high, some melting of surface fibersof the nonwoven web can also take place, which upon cooling provides aneven stronger bond between the polymeric precursor material and thenonwoven web.

In an another method, a polymeric precursor film can be applied to asurface of the nonwoven web by vacuum lamination of the precursor filmmaterial onto the modified web.

The resulting composite web structure can then be passed between a pairof opposed, interengaging forming rolls 16, 17 at modification station14. The forming rolls of station 16 can have a surface configuration anda structural arrangement similar to those forming rolls disclosedhereinabove. It is found that the interactions between the film and thenonwoven web during stretching promote “rapid nucleation” mode of poreformation in the film component. Without being bound by theory, it isbelieved that these interactions between the film and the nonwoven webare analogous to, but on a much finer scale, the contacts between theteeth and the web surface that provide nonuniform local strains and amultitude of neck regions, resulting in more uniform pore and capillarysizes. Additionally, the finer scale contacts in a laminate also renderthe laminate more responsive to factors that promote necking (e.g.,temperature).

An additional rolling step can be employed, if desired, to expand themodified composite web 18 laterally, to further reduce its basis weightand thereby its cost per unit area. The shapes of the teeth and grooves,the spacing of the axes of the forming rolls, and the degree ofinterengagement of the opposed teeth and grooves of the second set offorming rolls are such that the cross-web width of the exiting compositeweb is preferably from about 10% to about 200% of that of the enteringcomposite web, more preferably from about 10% to about 100%, and mostpreferably from about 10% to about 50%.

Modified Webs as Disposable Diaper Components

A modified web of the present invention typically provides a MVTR of atleast 2000 g/m²/24 hr, preferably at least 3000 g/m²/24 hr, and morepreferably at least 4000 g/m²/24 hr, and a dynamic fluid impact value ofless than 10 g/m², preferably less than 7 g/m², more preferably lessthan 5 g/m², and most preferably less than 3 g/m².

Another measure of fluid impermeability of the modified web is thebubble pressure. When the capillaries of the specimen are completelyfilled with a low surface tension fluid, there is essentially no airflow until sufficient air pressure is applied to force the fluid out ofthe largest capillaries in the specimen. The breakthrough pressure iscalled “bubble pressure” of the specimen, and is dependent on the sizeof the capillaries in the specimen. The larger size capillaries are theones more likely to permit fluids flow through during diaper wear. Amodified web of the present invention typically has a bubble pressure ofat least about 45 psi, preferably of at least 60 psi, and morepreferably of at least 70 psi.

Another measure of the breathability of the modified web is its abilityto allow air flow at moderate pressure differential across the web.Whereas MVTR is a measure of the convective flow of water moisture orair through the web, air flow is a measure of the forced flow of watermoisture or air through the web. Thus, air flow measurement simulatesthe conditions where a pressure is imposed on the absorbent article bywearer motions such as sitting, lying, bending, and the like. A modifiedfilm of the present invention typically has an air flow value, measuredat 20 psi differential pressure, of at least 2 liters/m²/s, preferablyof at least 3.5 liters/m²/s, and more preferably of at least 5liters/m²/s.

In forming a cloth-like, texturized web, the web is deformed orstretched beyond the elastic limit of the web, resulting in a pluralityof raised, rib-like elements. A measure of the increase in the web'ssurface contour length after the modification is the percent set. Toprovide the desirable comfort and fit of an article using the modifiedweb of the present invention, the modified web typically has a percentset value of at least about 20%, preferably at least about 40%, and morepreferably at least about 60%. In a preferred embodiment, the modifiedweb has a percent set value from about 40% to about 120%.

As noted previously herein, composite structures including a modifiedwebs and made in accordance with the present invention can beadvantageously utilized as a component of a disposable diaper. Thecomponent is generally the outermost component of the article, such as abacksheet, and provides imperviousness to the passage of liquid bodyexudates that are intended to be absorbed by and retained in anabsorptive component of the article. In the embodiment of a backsheet,the modified web provides desirable imperviousness to the passage offluids, while permitting passage therethrough moisture vapor and air.Additionally, as a backsheet, the modified web is preferably flexible,compliant, and has the desired soft, cloth-like outer surface texture.The ensuing discussion provides additional information relating to thestructure of such articles.

As used herein in the context of disposable absorbent articles, the term“absorbent article” refers generally to devices that absorb and containbody exudates. More specifically, it refers to devices that are placedagainst or in proximity to the body of a wearer to absorb and containthe various exudates discharged from the body. Exemplary absorbentarticles include diapers, training pants, feminine pads, pantiliners,and adult incontinence articles.

As used herein, the term “disposable” means absorbent articles that arenot intended to be laundered or otherwise restored or reused as anabsorbent article (i.e., they are intended to be discarded after asingle use and, preferably, to be recycled, composted, or otherwisedisposed of in an environmentally compatible manner).

An embodiment of a disposable absorbent article is shown in FIG. 15 inthe form of disposable diaper 200. As used herein, the term “diaper”refers to an absorbent article generally worn about the lower torso byinfants and incontinent persons. However, the present invention is alsoapplicable to other forms of absorbent articles, such as incontinencebriefs, incontinence undergarments, absorbent inserts, diaper holdersand liners, pull-on diapers and training pants, feminine hygienegarments, and the like.

FIG. 15 is a plan view of diaper 200 while in a flat-out state, and witha portion of the structure broken away to more clearly show the overallconstruction of the article. As it is represented in FIG. 15, theportion of diaper 200 that faces the body of the wearer faces away fromthe viewer of that Figure, and the portion of the diaper that facesoutwardly from the wearer, toward the wearer's outer garments, faces theviewer of FIG. 15. As shown, diaper 200 includes a liquid-pervioustopsheet 224; a liquid impervious backsheet 226; an absorbent core 228,which is preferably positioned between at least a portion of topsheet224 and backsheet 226; side panels 230; elasticized leg cuffs 232; anelastic waist feature 234; and a fastening system generally designated240.

Diaper 200 includes a chassis 222 that defines the main body of thediaper. Chassis 222 includes at least a portion of absorbent core 228,and also preferably includes outer covering layers formed by topsheet224 and backsheet 226. If the absorbent article includes a separateholder and a separate liner, chassis 222 generally also includes theholder and the liner. For example, a holder can include one or morelayers of material to form an outer cover of the article, and a linercan include an absorbent assembly including a topsheet, a backsheet, andan absorbent core. In such cases, the holder and/or the liner caninclude a fastening element that is used to hold the liner in placethroughout the time of use. For unitary absorbent articles, however,chassis 222 is the main structural component of the diaper, with otherfeatures added to form the overall diaper structure shown.

Backsheet 226 is generally that portion of diaper 200 that is positionedadjacent the garment facing surface 245 of absorbent core 228 and thatserves to prevent body exudates that are absorbed and contained inabsorbent core 228 from soiling articles that may come into contact withdiaper 200, such as bedsheets and undergarments.

Although topsheet 224, backsheet 226, and absorbent core 228 can beassembled in a variety of well-known configurations, preferred diaperconfigurations are described generally in U.S. Pat. No. 3,860,003,entitled “Contractible Side Portions for Disposable Diaper,” whichissued to Kenneth B. Buell on Jan. 14, 1975; U.S. Pat. No. 5,151,092,entitled “Absorbent Article with Dynamic Elastic Waist Feature Having aPredisposed Resilient Flexural Hinge,” which issued to Buell et al. onSep. 29, 1992; U.S. Pat. No. 5,221,274, entitled “Absorbent Article withDynamic Elastic Waist Feature Having a Predisposed Resilient FlexuralHinge,” which issued to Buell et al. on Jun. 22, 1993; U.S. Pat. No.5,554,145, entitled “Absorbent Article With Multiple Zone StructuralElastic-Like Film Web Extensible Waist Feature,” which issued to Roe etal. on Sep. 10, 1996; U.S. Pat. No. 5,569,234, entitled “DisposablePull-On Pant,” which issued to Buell et al. on Oct. 29, 1996; U.S. Pat.No. 5,580,411, entitled “Zero Scrap Method For Manufacturing Side PanelsFor Absorbent Articles,” which issued to Nease et al. on Dec. 3, 1996;and U.S. Pat. No. 5,899,895, entitled “Absorbent Article WithMulti-Directional Extensible Side Panels,” issued May 4, 1999, to Robleset al. The disclosures of each of the foregoing patents and patentapplication are incorporated herein by reference.

The modified web of the present invention can be employed as a backsheet226, as shown in FIG. 15. In one embodiment, the backsheet 226 may be afilm that is pervious to moisture vapor, preferably pervious to air, andalso substantially impervious to liquids, as hereinabove described. Forexample, a breathable film or a precursor film that is thereafterrendered breathable can be joined with a modified nonwoven, as describedearlier herein. A breathable backsheet can provide a barrier to thepassage of liquids through the backsheet while allowing the passage ofmoisture vapor, and preferably air, which increases the comfort to thewearer by enabling the reduction of the relative humidity level insidethe diaper as it is worn. in another embodiment, the backsheet can be acomposite backsheet formed from a film joined with a nonwoven web. Thenonwoven can be the outwardly-facing surface of the diaper for softnessand cloth-like external appearance, and the impervious film can providea barrier to prevent absorbed waste matter from contacting the clothingworn by a user, or from contacting bedding if worn by a user whilesleeping.

Test Methods

Components such as backsheets for disposable absorbent articlespreferably have moisture vapor transmission rates, dynamic fluid impactvalues, and desirably oxygen permeation rates that fall within preferredranges. The test methods for determining the values of those parametersfor particular materials are described below.

Moisture Vapor Transmission Rate Determination

One measure of the breathability of a film or composite material is theperviousness of the film or composite to the passage of water vapor,reflected by the moisture vapor transmission rate (MVTR) of the film. Inthe case of disposable diapers, breathability can be imparted to, forexample, a composite backsheet by the process hereinabove described, orby employing a film in the composite which already possesses such aquality, as also described hereinabove. In that regard, the MVTR of thecomposite material, such as a backsheet, is preferably from about 500g/m²/24 hr to about 5000 g/m²/24 hr, more preferably from about 1000g/m²/24 hr to about 4000 g/m²/24 hr, and most preferably from about 2000g/m²/24 hr to about 3000 g/m²/24 hr.

The MVTR can be determined by placing a quantity of a hydrophilicmaterial, such as calcium chloride, into a non-porous, open-top vessel(not shown) having an outwardly-extending flange around the vesselopening. A portion of the material for which the MVTR is to bedetermined is placed in overlying relationship relative to the vesselopening and is in contact with the flange of the vessel to completelycover the open end of the vessel. An annular gasket and an annularretaining ring are then placed over the material to be tested and aresecurely clamped to the vessel flange by any convenient clampingarrangement, to tightly and completely seal the periphery of the vesselopening in order that transmission of air or moisture vapor can onlyoccur through the material under test. The resulting assembly is thenweighed to determine the initial weight of the vessel and its contents.

After the initial weight has been determined, the assembly is placed ina chamber having a constant temperature (40° C.) and a constant humidity(75% relative humidity). The vessel is maintained under thoseatmospheric conditions for a period of five (5) hours, after which it isremoved from the chamber, wrapped tightly with an impervious film toprevent transfer of moisture into and out of the vessel, and is allowedto reach thermal equilibrium with the ambient atmosphere in which theweigh balance is located. Thermal equilibrium is achieved in about 30minutes, after which the film overwrap is removed from the vessel, whichis again weighed to determine the final weight of the vessel and itscontents.

The MVTR is calculated by the following formula, which provides the MVTRin g/m²/24 hr:

${MVTR} = \frac{\left( {{{Final}\mspace{14mu} {{Wt}({gm})}} - {{Initial}\mspace{14mu} {{Wt}({gm})}}} \right) \times 24.0}{{Sample}\mspace{14mu} {Area}\mspace{14mu} \left( {{sq}.\mspace{14mu} {meters}} \right) \times 5.0\mspace{14mu} {{hr}.}}$

Dynamic Fluid Impact Value Determination

When imparting a limited degree of moisture vapor, and also preferablyair perviousness to a component such as a backsheet, it is importantthat the imperviousness of the component to liquids is not significantlydiminished. And in addition to the desired attributes of imperviousnessto liquids and perviousness to moisture vapor and preferably air when acomponent such as a backsheet is under no-load conditions, it is alsodesirable that substantial liquid imperviousness of the component bemaintained even when the absorbent article is subjected to impact loads.Such loads can be imposed, for example, on a diaper backsheet when ababy wearing the diaper abruptly goes from a standing to a sittingposition. In that regard, it is preferred that the perviousness toliquids under impact conditions be less than about 10 g/m², morepreferably less than about 5 g/m², and most preferably less than about2.5 g/m².

Perviousness of a material under impact conditions can be assessed by atest the measures the dynamic impact value of the material. As referredto herein, the “dynamic impact value” of a material is a value that isbased upon the impact energy an average 20 lb. baby will impart to asaturated diaper if he or she falls or abruptly shifts from a standingposition to a sitting position. Essentially, the dynamic impact value isa measure of the quantity of liquid that penetrates through a materialunder impact conditions.

Determination of the dynamic impact value for a particular material canbe made by applying to the material an impact load of 20 Joules (14.75ft-lb.) over an area of about 13.5 in², or 2300 Joules/m². Impactloading of a test specimen can be performed in a number of ways, such asby a device 180 shown in FIG. 14. Device 180 includes a pivotable lever182 that has a weight 184 at its outer end. Weight 184 has an impactarea of 0.00317 m² to contact a test specimen 186. To simulate the skinand body fat of a baby a foam impact pad 188 is positioned on base 190of device 180 and opposite weight 184. A suitable foam pad is availablefrom American Excelsior Corp., of Cincinnati, Ohio, and is a 1 in thickpolyurethane foam pad undergoes 15.3% compression at a 1 psi. appliedload. Impact pad 188 is preferably a crosslinked rubber foam pad, about5 in. by 5 in., is carbon black filled, has a density of 0.1132 g/cm³,and has a thickness of 0.3125 in.

A wet diaper is simulated by providing a circular pad 192 in the form ofa 2.5 in diameter section of CMC517 material available from WeyerhaeuserInc. of Columbus, Miss. Pad 192 has a basis weight of 228 g/m², and acaliper of 0.127 in. measured under a 0.2 psi. load. The pad issaturated with simulated urine (Triton X-100, 0.0025% (wt/vol), andavailable from Union Carbide Corp., of Danbury, Conn.) so that thesaturated pad has a weight 10 times that of the dry pad.

Circular pad 192 is saturated and is held against the impact surface ofweight 184 by the material 184 for which the impact perviousness is tobe determined. In that regard, a 10 in. by 10 in. test sheet of materialcan be provided, with the outside surface of the material (i.e., thatsurface of the material which would be an outside surface of anabsorbent article) facing downwardly. Material 194 is applied over pad192 and is attached to the impact surface of weight 184 by a rubber band196, or the like.

Weight 184 is adapted to impact a piece of dry filter paper 198, whichcan, for example, be a filter paper obtained from Whatman Inc, ofHaverhill, MASS, (#2 filter paper, approximately 100 mm. diameter,Whatman Catalog No. 1002 150). The initial weight of the dry filterpaper is determined, and the filter is placed in position on energyabsorbing impact pad 188 that is positioned on base 190.

Weight 184 with its simulated diaper (saturated core 192 and overlyingbacksheet material 186) is dropped onto the filter paper from a heightcalculated to provide the desired impact load to the simulated diaper.Any liquid that passes through the material as a result of the impact isreceived on the filter paper. Weight 184 is permitted to remain in placeon filter paper 198 for a period of 2 minutes after impact. Thereafter,the impacted filter paper is placed on a scale, and when three minutesfrom the time of impact have elapsed the weight of the impacted filterpaper is determined. The dynamic impact value is calculated from thefollowing formula:

${DIV} = \frac{{Filter}\mspace{14mu} {Mass}\mspace{14mu} {Change}\mspace{14mu} ({grams})}{{Impact}\mspace{14mu} {Area}\mspace{14mu} \left( {{sq}.\mspace{14mu} {meters}} \right)}$

Air Flow Rate

The air flow rate of the material can be determined by placing a portionof the material between a sintered stainless steel disk (having highporosity and a pore size in the 5-10 μm range) and an annular gasket,and clamped securely into the testing fixture of a capillary flowporometer (available from PMI, Ithaca, N.Y.). The flow porometer isprogrammed to measure the air flow rate across the specimen over a rangeof applied air pressures. The air flow rate of the film is determined byreading the air flow rate at 20 psi. For this measurement to beaccurate, the air flow rate of the sintered stainless steel disk shouldbe more than 100 times greater than that measured for the specimen. Thespecimen's air flow rate is expressed as the air flow rate inliters/second divided by the sample area inside the annular gasket insquare meters.

Bubble Pressure

The bubble pressure of the material can be determined by completelyfilling the specimen's capillaries with a low surface tension Porewick™(available from PMI, Ithaca N.Y.), placing the saturated specimenbetween a sintered stainless steel disk and an annular gasket, andclamped securely into the testing fixture of a capillary flow porometer(available from PMI, Ithaca, N.Y.). The capillary flow porometer isprogrammed to record the bubble pressure at a flow rate of 50 cc/minuteand a V/PT factor of 30. For this measurement to be accurate, the poresof the sintered stainless steel disk should be greater than about threemicrons, and less than about 15 microns. The instrument records thespecimen's bubble pressure automatically.

Percent Set Measurement Method

Percent Set provides a measure of the increase in the web's surfacecontour length after modification. This measurement is done byactivating the web using the apparatus such as shown in FIG. 2. Beforemodification, a pair of lines 100 mm apart are drawn on the portion ofthe specimen perpendicular to the direction of web stretching. Asuitable tensile testing apparatus equipped with a force transducersensitive to small forces should be used. The grips (pneumaticallyactuated, flat-face type) are set to a gage length of 100 mm. Thespecimen is mounted so that the lines coincide with the edges of thegrips. The load-displacement data are collected at a cross-head speed of0.1 cm/second. The displacement at which the load increases above about5 grams/cm of sample width is recorded. The specimen's percent set isrecorded as

${\% \mspace{14mu} {set}} = {\frac{{displacement}({mm})}{100\mspace{14mu} {mm}} \times 100\%}$

For a pre-activated web, that is, the web has been stretched in apre-forming process prior to being modified by the forming process ofthe present invention, the percent set of the modified web is a“residual set”.

EXAMPLES Example 1

A polyethylene composition having calcium carbonate particles dispersedtherein is extruded using a conventional extruder. A film web is ofabout 49 gsm gauge. The film web is then incrementally stretchedaccording to the method disclosed herein and shown schematically onFIG. 1. The process uses 6 inch (15.24 cm) diameter forming rolls. Theweb and the tooling may be at ambient temperature or may be heated to ahigher temperature as indicated. TABLE I shows the processing parametersand the properties of the resultant breathable web. The forming rollshave the tooth and groove configuration of FIG. 2.

TABLE I EXAMPLE I-a I-b I-c I-d I-e I-f I-g Pitch (mm) 1.52 1.52 1.520.76 1.52 0.76 1.52 Engagement (mm) 1.02 1.02 1.57 0.76 1.57 0.76 1.57Total Applied Strain 75 75 140 140 140 140 140 (%) Web Speed 42 219 219219 42 42 219 (meters/min) Web Temperature 65 65 65 65 25 25 25 (C.)Engineering strain 93 480 770 1100 150 215 770 rate* (sec−1) MVTR(g/m²/day) 3300 2600 4100 4000 3200 3100 2900 Dynamic Fluid 5.4 2.7 1.84.0 1.8 3.0 0.5 Impact (gsm) Set (%) 30 30 72 93 66 65 66

Example 2

A precursor laminate of nonwoven and film is prepared via adhesivebonding. The nonwoven is a carded nonwoven web of bi-component fibershaving the configuration of a polyethylene sheath and a polypropylenecore is used. The nonwoven web has a gauge of 22 gsm. The precursor(i.e., unmodified) film is made from polyethylene/calcium carbonate andhas a gauge of about 46 gsm gauge, and is extrusion bonded to thenonwoven web. The unmodified laminate is incrementally stretchedaccording to the method disclosed herein. The process is shownschematically on FIG. 9. The process uses 6 inch (15.24 cm) diameterforming rolls. The web and the tooling may be heated to a sufficientlyhigh temperature as indicated. TABLE II shows the processing parametersand the properties of the resultant breathable web. The forming rollshave the tooth and groove configuration of FIG. 2.

TABLE II EXAMPLE II-a II-b II-c Pitch (mm) 1.52 1.52 0.76 Engagement(mm) 1.02 1.57 0.76 Total Applied Strain (%) 75 140 140 Web Speed(meters/min) 42 42 42 Web Temperature (C.) 65 65 65 Engineering strainrate* (sec−1) 93 150 215 MVTR (g/m²/day) 2300 3500 4000 Dynamic FluidImpact (gsm) 1.0 4.0 3.2 Set (%) 20 59 82

Example 3

The unmodified laminate of Example 2 is pre-activated by a two-stageforming process. The first stage is a CD stretching and the second stageis a MD stretching. The pre-activation process uses forming rolls havinga 6 inch (15.24 cm) diameter and a tooth and groove configuration ofFIG. 2, and is operated at a web speed of about 150 m/min and a webtemperature of about 60° C. The pre-activated laminate is then subjectedto the forming process according to the present invention. The web andthe tooling may be at ambient temperature or may be heated to a highertemperature as indicated. TABLE III shows the processing parameters andthe properties of the resultant breathable web. The forming rolls havethe tooth and groove configuration of FIG. 2.

TABLE III EXAMPLE III-a III-b III-c Pitch (mm) 0.76 0.76 0.76 Engagement(mm) 0.38 0.38 0.38 Total Applied Strain (%) 45 45 45 Web Speed(meters/min) 219 219 219 Web Temperature (C.) 25 65 95 Engineeringstrain rate* (sec−1) 500 500 500 MVTR (g/m²/day) 2300 2800 3100 DynamicFluid Impact (gsm) 1.4 1.8 1.6 Residual Set (%) 10 13 15

Example 4

The film web of Example 1 is incrementally stretched according to themethod disclosed herein and shown schematically on FIG. 1. The processuses 6 inch (15.24 cm) diameter forming rolls. The web and the toolingare heated to a temperature of 65° C. TABLE IV shows the processingparameters and the properties of the resultant breathable web. Theforming rolls have the tooth and groove configuration that produces amodified web as shown in FIG. 10.

TABLE IV EXAMPLE IV-a IV-b Pitch (mm) 1.02 1.02 Engagement (mm) 0.761.02 Total Applied Strain (%) 87 133 Web Speed (meters/min) 195 195 WebTemperature (C.) 65 65 Engineering strain rate* (sec−1) 600 810 MVTR(g/m²/day) 3800 4600 Dynamic Fluid Impact (gsm) 2.8 4.1

Example 5

An unmodified laminate is incrementally stretched according to themethod disclosed herein. The laminate included a carded nonwoven web ofpolypropylene fibers and a film of from polyethylene/calcium carbonate.The nonwoven web has a gauge of 18 gsm and the film has a gauge of about35 gsm gauge and is extrusion bonded to the nonwoven web. The processuses 6 inch (15.24 cm) diameter forming rolls. The web and the toolingare heated to 65° C. TABLE V shows the processing parameters and theproperties of the resultant breathable web. The forming rolls have thetooth and groove configuration that produces a modified web as shown onFIG. 10.

TABLE V EXAMPLE V-a V-b V-c V-d Pitch (mm) 1.02 1.02 0.76 1.02Engagement (mm) 0.64 0.76 1.02 1.02 Total Applied Strain (%) 66 87 87133 Web Speed (meters/min) 30 30 195 195 Web Temperature (C.) 65 65 6565 Engineering strain rate* (sec−1) 74 92 600 810 MVTR (g/m²/day) 27003900 2700 3500 Dynamic Fluid Impact (gsm) 2.4 4.3 2.4 6.1

Example VI

This example illustrates that suitable control of process parameters canlead to an especially desirable properties in the resultant film webs.TABLE VI below illustrates the effect of process conditions and thebeneficial properties of the resultant material. The material subjectedto the process is a polyolefin/calcium carbonate film of 49 g/m².

Example Example VI-a VI-b Pitch (mm) 0.76 0.76 Engagement (mm) 0.51 0.76Total Applied Strain (%) 75 140 Web Speed (meters/min) 42 216 WebTemperature (C.) 65 25 Engineering strain rate* (sec−1) 140 1100 MVTR(g/m²/day) 3300 2500 Dynamic Fluid Impact (gsm) 2.3 2 Air Flow (l/m²/s)2.2 3.9 Bubble Pressure (psi) 74.8 77.7 Set (%) 40 63

All documents cited in the Detailed Description of the Invention are, inrelevant part, incorporated herein by reference; the citation of anydocument is not to be construed as an admission that it is prior artwith respect to the present invention.

While particular embodiments of the present invention have beenillustrated and described, it would be obvious to those skilled in theart that various changes and modifications can be made without departingfrom the spirit and scope of the invention. It is therefore intended tocover in the appended claims all such changes and modifications that arewithin the scope of this invention.

What is claimed is:
 1. A disposable absorbent article comprising: a) avapor permeable, liquid impervious, backsheet laminate; b) a liquidpervious topsheet which is positioned in facing relation with saidbacksheet; c) an absorbent core located between the backsheet laminateand the topsheet; wherein a backsheet film is joined to a nonwoven toform the vapor permeable, liquid impermeable, microporous backsheetlaminate; wherein the vapor permeable, liquid impermeable, microporousbacksheet laminate has a dynamic fluid impact value of less than about10 g/m²; wherein the backsheet film comprises a plurality pores and aplurality of capillaries running therebetween and connecting theplurality of pores; wherein the plurality of capillaries run in a commondirection; wherein the modified backsheet film is from about 0.25 milsto about 2.5 mils.
 2. The disposable absorbent article of claim 1,wherein the vapor permeable, liquid impermeable, microporous backsheetlaminate has an air flow rate of at least about 2 liters/m²/s.
 3. Thedisposable absorbent article of claim 1, wherein the backsheet filmfurther comprises a plurality of first regions and a plurality of secondregions adjacent to said first regions, wherein the second regionscomprise raised rib-like elements.
 4. The disposable absorbent articleof claim 3, wherein the backsheet film has a percent set of at leastabout 40 percent.
 5. The disposable absorbent article of claim 1,wherein the vapor permeable, liquid impervious, backsheet laminate ismodified such that it comprises a pattern of deformed areas.
 6. Thedisposable absorbent article of claim 1, wherein the backsheet filmcomprises pore forming agents and has a mean pore size less than about0.3 microns.
 7. The disposable absorbent article of claim 1, wherein thebacksheet film comprises a thermoplastic polymer selected from the groupconsisting of polyolefins and copolymers, polyesters and copolymers,polyurethanes and copolymers, polyamides and copolymers and mixturesthereof.
 8. The disposable absorbent article of claim 1, wherein thevapor permeable, liquid impermeable, microporous backsheet laminatecomprises fibers selected from the group consisting of polyolefins andcopolymers, polyesters and copolymers, polyamide and copolymers,cellulose derivatives, and mixtures thereof.
 9. The disposable absorbentarticle of claim 5, wherein the pattern of deformed areas comprisealternating rows of peaks and valleys.
 10. The disposable absorbentarticle of claim 1, wherein a plurality of micropores of the backsheetfilm are elongated.
 11. The disposable absorbent article of claim 10,wherein the plurality of micropores are elongated in the machinedirection.
 12. The disposable absorbent article of claim 10, wherein thepeaks and the valleys of the deformed areas are thicker thanintermediate portions disposed between the peaks and the valleys. 13.The disposable absorbent article of claim 12, wherein the intermediateportions are more breathable versus other portions of the backsheetfilm.
 14. The disposable absorbent article of claim 1, wherein theplurality of capillaries of the backsheet film is less than 0.2 microns.15. The disposable absorbent article of claim 1, wherein the pluralityof capillaries of the backsheet film is less than 0.1 micron.
 16. Thedisposable absorbent article of claim 1, wherein micropores of backsheetfilm are generally uniform in size.
 17. The disposable absorbent articleof claim 9, wherein the backsheet film is modified by beingincrementally stretched.
 18. The disposable absorbent article of claim1, wherein a plurality of capillaries of the backsheet film arehydrophobic.
 19. The disposable absorbent article of claim 1, whereinthe vapor permeable, liquid impervious microporous backsheet laminatecomprises a dynamic fluid impact value of less than about 7 g/m². 20.The disposable absorbent article of claim 1, wherein a majority of thecapillaries run in a common direction.